1. Field of the Invention
The present invention relates generally to an ink furnishing apparatus for a printing press. More specifically, the invention relates to an ink furnishing apparatus, in which ink-furnishing is performed in a keyless ink furnishing mode, i.e. overall area ink-furnishing mode, for furnishing an ink adjusted into substantially uniform thickness on the overall surface of a printing plate, and a non-keyless ink furnishing mode, i.e. partial area ink-furnishing mode for furnishing an ink in an amount determined corresponding to an area of the image on the divided partial area of the printing plate divided along the axial direction of a plate cylinder, selectively. Also, the invention relates to an ink furnishing apparatus which is adapted to an ink having relatively high viscosity.
2. Description of the Related Art
As disclosed in Japanese Unexamined Patent Publication (Kokai) No. Heisei 1-93397, for example, the conventional keyless ink furnishing apparatus furnishes an ink over the entire surface of the printing plate in substantially uniformly by carrying the ink in an ink pan by rotating an ink fountain roller partially dipped in the ink within the ink pan, transferring the ink to a metering roller of downstream side, scraping out an excess amount of the ink by means of a doctor blade contacting on the peripheral surface of the metering roller to limit a furnishing ink amount in an amount determined by a capacity of a large number of metering cells (recesses) provided on the overall surface of the metering roller for furnishing substantially uniform amount of the ink.
On the other hand, Japanese Unexamined Patent Publication No. Heisei 2-106350 and Japanese Unexamined Patent Publication No. Heisei 2-122994 discloses another keyless ink furnishing apparatus different from the keyless ink furnishing apparatus disclosed in Japanese Unexamined Patent Publication No. Heisei 1-93397. However, as far as an ink furnishing apparatus carrying the ink stored in a storage means with the peripheral surface of the fountain roller by rotation thereof, is concerned, they have substantially the similar construction to Japanese Unexamined Patent Publication No. Heisei 1-93397 for carrying the ink upwardly from the ink storage means.
However, while the conventional keyless ink furnishing apparatus is adapted to low viscous ink, when high viscous ink is used, adhering ability of the ink on the peripheral surface of the fountain roller is low in comparison with the low viscous ink. Thus, amount of the ink carried upwardly with the peripheral surface of the fountain roller becomes insufficient to make it impossible to effectively furnish the ink.
Commonly owned Japanese Examined Patent Publication (Kokoku) No. Heisei 7-45244 proposes a high viscous ink adapted type keyless ink furnishing apparatus adapted to relatively high viscous ink, in which an ink contained in an ink fountain formed by a tilted plate and the periphery of the fountain roller, is carried out from a gap defined between the peripheral surface of the fountain roller and the lower end of the tilted plate by rotating the fountain roller.
However, the high viscous adapted type keyless ink furnishing apparatus sill hold problems, such as splashing of ink or so forth to be solved.
At first, splashing of ink is caused for opposite directions of rotation between the fountain roller and a downstream side roller to cause movement of the peripheral surfaces of the rollers in mutually opposite directions. When the ink is transferred between the peripheral surfaces of the rollers moving in opposite directions, splashing of the ink is caused. Particularly, higher rotation speed of the rollers results in greater ink splashing amount to lower ink furnishing efficiency and to stain the environment.
Next, when the high viscous ink adapted type keyless ink furnishing apparatus is applied to a lithographic press, in which printing is performed utilizing dampening water, the dampening water penetrates into an ink furnishing path. Since the apparatus has no mechanism for mixing the penetrated dampening water and the ink or mechanism for removing the mixture of the dampening water and the ink, the dampening water and ink are present in the ink furnishing apparatus in the separated condition. This water may be a cause of stripping of the roller to make ink furnishing impossible.
On the other hand, the most important advantage common to all of the keyless ink furnishing apparatus set forth above, i.e. the function for constantly furnishing of ink in substantially uniform thickness over the entire surface of the printing plate without adjustment by ink adjustment key, may serve as disadvantage for color printing by using of high viscous ink. Namely, in the current printing businesses, in the color printing utilizing relatively high viscous ink, it is frequently required to locally furnishing ink for quite limited portion on the printing surface as a spot color printing and is not required to furnish the ink over the entire printing surface. In such case, when the conventional keyless ink furnishing apparatus is used, the ink is inherently furnished even for the portion where furnishing of ink is not required. Therefore, large amount of ink should be wasted. Furthermore, furnishing the ink in the extra areas inherently require cleaning of unnecessarily large area to waste labour and time to degrade efficiency of printing operation.
In addition, there are demand for printing of special color other than three primary colors (yellow, cyan and magenta) or black with an ink having higher viscosity than the normal ink, for high quality printing superior in complexion and volume utilizing three primary color inks and/or black ink of higher viscosity than that of the normal ink. For performing printing with satisfying such demands, a printing facility for high quality printing becomes necessary for difficulty of application of a printing facility employing the conventional keyless ink furnishing. Therefore, in order to perform both paintings, it is required to have two kinds of mutually different printing facilities to be wasteful in viewpoint of installation space, investment for the apparatus.